Mechanical timers used in domestic applicances and on certain industrial equipment must be low cost devices. Mechanical hand set timers have been developed for this market. Such a timer is shown in U.S. Pat. No. 3,568,429, wherein a motor is mounted on a housing to drive a cam that actuates a standard, purchased switch when the position of the cam indicates expiration of certain time. A knob moves the cam into a set time position which energizes the motor and causes the motor to drive the cam until the switch actuated position is reached. At that time, the switch is actuated and the motor is de-energized. When the cycle is concluded, the external circuit being controlled is either activated or de-activated in accordance with the function of the timer switch in the circuit. For background purposes, the prior U.S. patent is incorporated by reference herein.
The primary requirements of a mechanical hand set timer of the type to which the present invention is directed is low cost and dependable operation. Three of the primary cost factors in mass production of the hand set timers are the cost of assembly, the need for separate, purchased switches and the need for an arrangement to change the switching functions of the timer to produce a normally closed, normally opened, and/or double throw switching function. A substantial amount of effort has been devoted to reduce the cost of these three items in mechanical hand set timers for commercial application.